Free Shipping Tool

Box Size &
DIM Weight Calculator

Find the right box size and calculate dimensional weight for UPS, FedEx, USPS, and DHL instantly. Avoid overpaying by right-sizing your packaging.

All 4 major carriers — compare side by side

Imperial & metric — auto-converts units

Size limit checks — avoid oversize fees

Custom DIM factors — for negotiated rates

DIM Weight Formula

(L × W × H) ÷ Factor

UPS/FedEx: 139 • USPS: 166

Dimensional Weight Calculator

Calculate DIM weight for UPS, FedEx, USPS, and DHL

Length (in)

Width (in)

Height (in)

Actual Weight (lb)

Volume

960 in³

Girth: 36.0 in | Length + Girth: 48.0 in

UPS

DIM Factor: 139

Actual Weight:5 lb

DIM Weight:7 lb

Billed Weight:7 lb

Using DIM weight

FedEx

DIM Factor: 139

Actual Weight:5 lb

DIM Weight:7 lb

Billed Weight:7 lb

Using DIM weight

USPS

DIM Factor: 166

Actual Weight:5 lb

DIM Weight:5.8 lb

Billed Weight:5.8 lb

Using DIM weight

Official Carrier Rate Calculators

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UPS Rate Calculator

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FedEx Rate Calculator

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Get FedEx Ground, Express, and Freight shipping rates with delivery estimates.

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USPS Postage Calculator

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Calculate USPS Priority Mail, First-Class, and Ground Advantage rates.

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Pro Tip: Use our calculator above to determine DIM weight first, then enter the billed weight (the higher of actual or DIM weight) into carrier calculators for accurate shipping quotes.

How Dimensional Weight Works

The DIM Weight Formula

DIM Weight =(L × W × H) ÷DIM Factor

Step 1: Measure

Measure the length, width, and height of your package in inches (or cm for metric).

Step 2: Calculate

Multiply L × W × H, then divide by the carrier's DIM factor (139 or 166).

Step 3: Compare

Your billed weight is the greater of actual weight or DIM weight.

Example Calculation

Package: 18" × 14" × 10" box weighing 8 lbs

Volume = 18 × 14 × 10 = 2,520 cubic inches

UPS/FedEx DIM Weight = 2,520 ÷ 139 = 18.1 lbs

USPS DIM Weight = 2,520 ÷ 166 = 15.2 lbs

Result: Even though the package only weighs 8 lbs, UPS and FedEx will charge based on the 18.1 lb DIM weight. USPS would charge based on 15.2 lbs (for Zones 5-9) or 8 lbs actual weight (for Zones 1-4).

Carrier DIM Factors & Size Limits

Compare dimensional weight factors and maximum package sizes across major carriers. A lower DIM factor means higher calculated DIM weight and potentially higher shipping costs.

Carrier	DIM Factor (in³/lb)	DIM Factor (cm³/kg)	Max Weight	Max Length	Max L+G	Notes
UPS	139	5,000	150 lb / 70 kg	108" / 274 cm	165" / 419 cm	DIM applies to all packages
FedEx	139	5,000	150 lb / 68 kg	119" / 302 cm	165" / 419 cm	DIM applies to all packages
USPS	166	5,000	70 lb / 31.75 kg	108" / 274 cm	130" / 330 cm	DIM only for Zones 5-9
DHL Express	139	5,000	150 lb / 70 kg	118" / 300 cm	157" / 400 cm	International standard

Higher factor = Lower DIM weight = Better for you

Lower factor = Higher DIM weight = More expensive

Tips to Reduce DIM Weight Charges

Right-Size Your Packaging

Use the smallest box that safely holds your product. Every extra inch of air space increases your DIM weight. Consider multiple box sizes rather than one-size-fits-all.

Use Poly Mailers When Possible

For soft goods like clothing, poly mailers conform to the product shape and dramatically reduce DIM weight compared to boxes. Padded mailers work well for small, fragile items.

Consider USPS for Nearby Zones

USPS doesn't apply DIM pricing to Zones 1-4 shipments. For lightweight, bulky items going short distances, USPS Priority Mail can be significantly cheaper than UPS or FedEx.

Split Large Orders

Sometimes shipping two smaller packages is cheaper than one large box. Use our calculator to compare scenarios before committing to packaging.

Negotiate DIM Factors

High-volume shippers can often negotiate better DIM factors with carriers. Even moving from 139 to 166 can mean significant savings on lightweight, bulky shipments.

Use Custom Packaging

For products you ship repeatedly, custom boxes that perfectly fit your product eliminate wasted space and reduce DIM weight charges over time.

Box Size Recommender

Enter your product dimensions and weight to find the best standard box, check USPS Flat Rate eligibility, and see if a poly mailer works.

Enter Product Dimensions

Length (in)

Width (in)

Height (in)

Product Weight (lbs)

Padding Needed

Common Shipping Box Sizes

Standard corrugated box sizes available from most packaging suppliers.

Size (L x W x H)	Best For	DIM Weight
6 x 6 x 6"	Small items, mugs, candles	2 lbs
8 x 6 x 4"	Books, small electronics	2 lbs
10 x 8 x 6"	Shoes, medium products	4 lbs
12 x 10 x 8"	Multiple items, clothing bundles	7 lbs
14 x 14 x 14"	Large items, helmets, lamps	20 lbs
18 x 14 x 12"	Bulk shipments, large electronics	22 lbs
24 x 18 x 18"	Oversized items, home goods	56 lbs

USPS Flat Rate Box Guide

Flat Rate boxes ship for one price regardless of weight or distance. USPS provides the boxes for free at any post office.

Box	Dimensions	Price
Small Flat Rate Box	8-5/8" x 5-3/8" x 1-5/8"	$10.40
Medium Flat Rate Box (Top)	11" x 8.5" x 5.5"	$17.10
Medium Flat Rate Box (Side)	13-5/8" x 11-7/8" x 3-3/8"	$17.10
Large Flat Rate Box	12" x 12" x 5.5"	$22.45
APO/FPO Large Flat Rate Box	12" x 12" x 5.5"	$21.15

Frequently Asked Questions

What is dimensional weight (DIM weight)?

Dimensional weight, also known as volumetric weight or DIM weight, is a pricing technique used by shipping carriers. It calculates a theoretical weight based on package dimensions rather than actual weight. Carriers charge the greater of actual weight or DIM weight, ensuring they're compensated for the space a package occupies in their vehicles.

How do I calculate dimensional weight?

To calculate DIM weight, multiply Length × Width × Height to get the cubic volume, then divide by the carrier's DIM factor. For example, a 12" × 10" × 8" package with UPS (DIM factor 139) would be: (12 × 10 × 8) ÷ 139 = 6.9 lbs DIM weight. The billed weight is whichever is higher: actual weight or DIM weight.

What are the DIM factors for UPS, FedEx, and USPS?

UPS and FedEx both use a DIM factor of 139 (cubic inches per pound) for all packages. USPS uses a more favorable DIM factor of 166, but only applies dimensional pricing to Priority Mail and Priority Mail Express shipments going to Zones 5-9. For packages going to closer zones, USPS charges based on actual weight only.

Why did carriers change DIM factors?

In 2015, UPS and FedEx began applying dimensional pricing to all ground shipments (previously only applied to packages over 3 cubic feet). In 2017, they lowered the DIM factor from 166 to 139, increasing the calculated DIM weight and shipping costs. This was done to account for the increasing volume of e-commerce shipments that are lightweight but take up significant space.

How can I reduce dimensional weight charges?

To minimize DIM weight charges: 1) Use the smallest box possible that safely fits your product, 2) Consider custom-sized packaging for frequently shipped items, 3) Use poly mailers or padded envelopes for soft goods, 4) Break up large orders into multiple smaller packages if it reduces total DIM weight, 5) Choose USPS for lightweight, bulky items going to nearby zones.

What is the difference between girth and length + girth?

Girth is calculated as 2 × (Width + Height), measuring the circumference around the package's cross-section. Length + Girth is the longest dimension plus the girth. Carriers have maximum limits on both: UPS and FedEx allow up to 165" for Length + Girth, while USPS limits it to 130". Exceeding these limits requires special handling or may make the package unshippable.

Does USPS always charge dimensional weight?

No, USPS only applies dimensional pricing to Priority Mail and Priority Mail Express packages shipped to Zones 5-9. For Zones 1-4 (shorter distances), USPS charges based on actual weight only. This makes USPS a cost-effective choice for lightweight, bulky packages being shipped nearby. First-Class Package Service and USPS Ground Advantage do not use DIM pricing.

How do I convert between imperial and metric measurements?

For length: 1 inch = 2.54 cm, or 1 cm = 0.3937 inches. For weight: 1 pound = 0.4536 kg, or 1 kg = 2.205 lbs. Our calculator automatically converts between systems when you toggle the unit switch. For DIM factors, the metric equivalent of 139 (in/lb) is approximately 5000 (cm/kg).

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